Optical pulses, a fresh of light or a packets of photons localized in time, sounds like a simple concept but it is very complex. Currently, femtosecond pulses and attosecond pulses can be produced by specialized laser systems.

By Heisenberg Uncertainty Principle, optical pulses are naturally broadband (in frequency). The pulses contains many different frequencies.

Because there are many different frequency, each frequency can propagate at different speed in a medium, leading to temporal distortion of pulses. This temporal distortion can be described by a function of frequency f(nu), or spectral phase.

Human eye has a response time of ~30 ms, which certainly cannot see any distortion of pulses.

So I wrote a matlab code, hoping to feel temporal distortion of pulses, making it a more tangiable concept.

Specifically, I convert the optical frequency into acoustic frequency that human can hear.

I simulated "Chirped sound" with instantaneous frequency that change linearly with time. Chirped is a temporal distortion very common to optical pulses, described by a quadratic spectral phase.

A typical femtosecond pulse (fs = 10^(-15) s) with chirp looks like the following image (the Electric field oscillate faster on the left side compared to the right side)